Generally, a coaxial cable is frequently used for transmission of RF signals such as cable TV signals and cellular phone broadcasting signals.
The coaxial cable includes a central conductor, an outer conductor coaxially formed on the central conductor, a dielectric layer formed between the central conductor and the outer conductor, and a sheath surrounding the outer conductor.
In case a signal is transmitted using the above coaxial cable, a loss of transmitted signal occurs due to electric conductivities of the central conductor and the outer conductor and a dielectric constant of the dielectric layer. Thus, when making a coaxial cable, it is most important to effectively reduce a transmission loss.
Conventionally, a method of improving a shielding performance was frequently used in order to reduce a transmission loss. In detail, in most cases, a dimension structure of the central conductor and the outer conductor was improved in the designing step so as to reduce a dielectric constant of the dielectric layer, a dielectric characteristic of the dielectric substance was improved, or a shielding characteristic of the outer conductor was reinforced.
However, the above methods are advantageous in reducing a transmission loss of a coaxial cable by improving a shielding performance, but they cannot directly improve transmission characteristics of the central conductor and the outer conductor.